Bandsaw Mill Continuted
A continuation of the design of my Bandsaw Mill. Be sure to read the first part of the Bandsaw Mill design
Wheel Block
I designed the wheel blocks to be made of multiple pieces of wood. I did this so I could orient the grain for strength. I will refer to the pieces by their number as shown is the picture below.
Pieces #1, #2, and #3 have a 5/8″ hole for the axle bolt. I set up a jig on my drill press to make sure that the hole got drilled in each piece correctly. You can see my penciled in arrow on piece #1. I had to shim piece #3 in the jig with a piece of wood equal to the bolt head thickness. Pieces #1 and #2 are oriented so that their end grain is not load bearing. Notice that piece #5, the one that receives the tensioning bolt, is screwed into and glued against edge grain of #1 and #2. Piece #3 has its grain running 90° to #1 and #2 so this makes the whole block a 3-ply… just really thick plywood.
Piece #5 is fancy compared to the others. I first drilled a small guide hole all the way through the center of the block. Then I drilled a recess for the washer with a forstner bit on each side. The inside I drilled a second time and then cleaned up with a chisel to create the slot for the washer. With the large holes cut, I switched to a 5/8″ forstner bit and drilled all the way through. To complete the block it was off to the bandsaw to cut the material out to finish the bolt slot. To keep the bolt from turning, i drilled and tapped for a 1/4″ bolt. The tension bolt slides in and the outer washer is held on with a small screw. The outer washer acts as a retaining clip to hold the bolt into the block.
The way I assemble is a bit different than most of the guys/gals I watch on youtube. Most of them glue and use a hundred clamps, then might put in some screws to “hold while the glue sets”. The first thing I did was to line up #1-3-2, insert a 5/8″ bolt, and thread on a nut to sandwich everything together. Once satisfied that those parts are lined up, I drill pilot holes and put in screws. I take it apart, then lather on some glue, get the screws started to where they just poke out a bit so they index into their holes, lightly clamp, then drive the screws.
Observations about the wheel block. At first I couldn’t get a hold of a 10″ long bolt. So I had to improvise with a shorter one. This lead to me having to drill out a larger hole in all of #2 and most of #3. This was a BAD situation. There is a tremendous amount of stress transferred to the axle and wheel block. I only had 2″ of pine supporting that load and that lead to the axle widening the hole and creating cracks in the block. Once I had a 10″ long bolt things worked much better since I could create the “sandwich” I intended to have all along. I really should make a new block with the 5/8″ hole only.
Tensioning and Tracking
Tensioning is done with a coupling nut on the bolt, there is no spring. I used a coupling nut to have as many threads as possible engaged on the bolt to try and prevent thread damage. When the wheel block is almost at full travel and the blade is tight, the coupling nut is almost completely filled with bolt thread.
It took me a while to decide how to do the tracking adjustment. I thought about having another bolt threaded into the wheel block, but since the block moves the tracking pressure point would also change. Then I had the brilliant idea to use a modified stop collar. I drilled out the threads of the stop collar to 5/16″, I cut the head off a 5/16″ bolt, put the bolt into the collar, and drilled a small hole to hold my finish nail pin. There is a piece of metal on the back of the main beam that allows the bolt to be shortened by tightening a nut. The beauty of this setup is that the tracking adjustment doesn’t have to move along the travel of the wheel block. There is enough slop between the tension bolt, collar, and tracking bolt to deal with the changing angle as the tracking nut is tightened.
Blade Guides
I created a video about my blade guides.
[embedyt] https://www.youtube.com/watch?v=ahm3wgoGlwA[/embedyt]
I use the roller guide style found on commercial mills. I didn’t want to spend a lot of money on “real” ones, so I made my own with a 5/8″ bolt (head ground down to match the bushing), a 3/4″ long 5/8″ ID bushing, a 3/4″ washer since it mates nicely to the bushing, and a stop collar to sandwich the assembly together. That gets put into a block that has (2) 5/8″ bearings. The block is adjustable up and down on a second block that attaches to the bottom of the beam. The second block is adjustable in/out from the back of the blade. I attach the block to the beam with a 5/16″ bolt that is threaded into a brass insert in the beam. I can adjust the blade guide location along the beam with the other inserts I installed. I figure that I don’t need infinite adjustment in blade guide location. Being able to move the guides on 12″ intervals is good enough.
Conclusion
While I wouldn’t want to use this mill for commercial milling, it is more than adequate for weekend warrior hobbyist activities. There are some adjustments that I need to make to improve the performance, but the bottom line is it gets the job done.